JPH07272974A - Biaxially oriented polyester film for capacitor - Google Patents

Abstract

PURPOSE:To provide a capacitor base film which has excellent withstand voltage characteristics and moisture and heat proof characteristics and contributes to the long-term reliability of the capacitor. CONSTITUTION:A biaxially oriented polyester film contains 0.1-2wt.% crosslinked polymer grains which has 0.1-2mum average grain diameter, 1.0-1.2 spherical ratio and 1.05-2.5 grain deformation after film biaxial orientation. The biaxial oriented polyester film for capacitor has a coating layer formed of water soluble or water dispersible resin at least on one plane of the film, has 0.005-0.5mum coating layer surface roughness Ra and 5mum or less total thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially stretched polyester film for metal-deposited film capacitors, which has excellent withstand voltage characteristics and wet heat resistance characteristics.

[0002]

2. Description of the Related Art Polyester films typified by polyethylene terephthalate are widely used as base films for capacitors because they have excellent mechanical properties, heat resistance and electrical properties. . However, with the recent development of various electric appliances and electronic devices, there is a demand for miniaturization and long-term reliability of capacitors, as well as higher characteristics. As the items required to have such high characteristics, firstly, there is a great improvement in withstand voltage characteristics, and secondly, there is an improvement in long-term wet heat resistance stability. Generally, in a polyester film for capacitors, it is essential to improve the running property of the film in order to improve workability in the process of forming a capacitor, and particles are contained in the film to achieve such an object. However, due to such particles, coarse projections are generated on the film surface, or when voids called voids are generated between the particles and the polyester film, it may lead to a defect such as withstand voltage reduction as a capacitor. Are known. Further, in general, the metal vapor-deposited polyester film has a drawback that the adhesiveness between the base film and the vapor-deposited metal, particularly the adhesiveness in a high temperature and high humidity environment, that is, the so-called wet heat resistance is poor. Therefore, when a film capacitor manufactured by using such a metal vapor-deposited polyester film is placed under high temperature and high humidity, moisture permeates at the interface between the base film and the vapor-deposited metal, and the capacitance of the capacitor decreases with time. There was a problem, and in terms of long-term stability, there was a need to improve the moisture and heat resistance of capacitors.

[0003]

Means for Solving the Problems The inventors of the present invention have made extensive studies in view of the above problems, and as a result, have made a capacitor using a biaxially stretched polyester film containing certain particles and having a certain coating layer. It was found that the device can exhibit excellent withstand voltage characteristics and wet heat resistance, and completed the present invention.

That is, the gist of the present invention is that the average particle size is 0.1 to 2 μm, the spherical ratio is 1.0 to 1.2, and the degree of particle deformation after biaxial stretching of the film is 1.05 to 2.5. A biaxially stretched polyester film containing 0.1 to 2% by weight of certain cross-linked polymer particles, having a coating layer made of a water-soluble or water-dispersible resin on at least one surface of the film, and the coating layer surface roughness Ra. Is 0.005 to 0.5 μm, and the total thickness is 5 μm or less.

The present invention will be described in more detail below. The polyester in the present invention means a repeating structural unit of 8
0 mol% or more indicates a polyester having ethylene terephthalate units or ethylene-2,6-naphthalate units. Further, the biaxially stretched polyester film of the present invention refers to a biaxially oriented polyester film using such polyester as a starting material, and a known method can be adopted as a production method thereof. For example, usually 270-33
After melt-extruding into a sheet at 0 ° C., cooling and solidifying at 40 to 80 ° C. to form an amorphous sheet, and then sequentially or vertically at 80 to 170 ° C. to obtain an area ratio of 4 to 20 times or A method in which biaxial stretching is performed at the same time and then heat treatment is performed at 150 to 270 ° C. can be adopted. When stretching in the machine and transverse directions, each may be stretched in one stage, or may be stretched in multiple stages as necessary, or a heat treatment section for relaxing orientation may be provided between the multi-stage stretches.

The first feature of the present invention is that the particles contained in the polyester film have an average particle size of 0.1 to 2 μm.
m, a spherical ratio of 1.0 to 1.2, and a degree of particle deformation after biaxially stretching the film of 1.05 to 2.5, the crosslinked polymer particles are contained in the film in an amount of 0.1 to 2% by weight. . When the average particle size is less than 0.1 μm, the running property of the polyester film is insufficient, which is not preferable. The average particle size is 2μ
If it exceeds m, the surface property of the film is deteriorated and the withstand voltage characteristic when used as a capacitor is poor, which is not preferable. The average particle size of the crosslinked polymer particles used is preferably 0.2 to 1.5.
μm, and more preferably 0.3 to 1.2 μm. If the degree of deformation of the particles after biaxially stretching the film is less than 1.05,
Voids are generated between the crosslinked polymer particles and the polyester film, and the particles fall off from the film, resulting in insufficient running properties of the film, or poor withstand voltage characteristics when used as a capacitor. Is not preferable.
On the other hand, when the deformation degree exceeds 2.5, the running property of the film is insufficient, which is not preferable. The degree of deformation of such particles is 1.2.
The range of -2.0, and more preferably 1.2-1.5 is preferable.

When the content of the crosslinked polymer particles in the film is less than 0.1% by weight, the running property of the film is insufficient, which is not preferable. On the other hand, if the content of the crosslinked polymer particles in the film exceeds 2% by weight, the surface property of the film is deteriorated and the withstand voltage characteristic when used as a capacitor is poor, which is not preferable. The method for producing the crosslinked polymer particles used in the present invention is not particularly limited, but as a typical example, only 1
One or more monobiaxial compounds (A) having one aliphatic unsaturated bond and one or more compounds (B) having two or more aliphatic unsaturated bonds in the molecule as a crosslinking agent It is better to apply a so-called emulsion polymerization method. Further, one or more compounds (C) having an ethylene glycol unit in the molecule may be added. The emulsion polymerization method here means emulsion polymerization in a broad sense including concepts such as soap-free emulsion polymerization and seed emulsion polymerization.

Examples of the compound (A) include acrylic acid, methacrylic acid and their alkyl or glycidyl esters, maleic anhydride and its alkyl derivatives, vinyl glycidyl ether, vinyl acetate, styrene and alkyl-substituted styrene. Examples of the compound (B) include divinylbenzene and divinylsulfone. Examples of the compound (C) include ethylene glycol monoacrylate, ethylene glycol methacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate and the like. The crosslinked polymer particles used in the present invention have a tendency that the affinity between the particles and the polyester is poor if the degree of crosslinking is too large, and conversely if the degree of crosslinking is too small, the heat resistance of the particles and the degree of deformation in the film are large. Sometimes it becomes too much. Therefore, in order to satisfy both of them, the weight ratio of the compound (B) as a crosslinking agent in the particles is preferably 10 to 70%, more preferably 20 to 60%, and particularly preferably 20 to 50%.

The content of ethylene glycol units in the crosslinked polymer particles is usually 3% by weight or more, preferably 5% by weight or more. Content of ethylene glycol unit is 3
If it is less than wt%, the affinity between the particles and polyester and the dispersibility in polyester may be insufficient. One embodiment of producing the crosslinked polymer particles in the present invention is as follows. That is, after dissolving a predetermined amount of a water-soluble polymerization initiator such as hydrogen peroxide or potassium persulfate in an aqueous medium, a predetermined amount of a mixed solution of the compounds (A), (B) and (C) Is added. After that, the reaction is carried out at a temperature not lower than the decomposition start temperature of the polymerization initiator, preferably at 30 to 90 ° C. for about 3 to 10 hours with stirring. At that time, depending on the monomer composition, some aggregated particles may be generated, and in this case, a dispersion stabilizer such as an emulsifier may be added in order to maintain the dispersion stability of the particles. First, the compounds (A) and (B)
To produce a core particle, and then to produce a double-structured crosslinked polymer particle in which an outer layer comprising the compounds (A), (B) and (C) is formed on the surface of the core particle. it can. The particles having such a double structure can easily have a relatively large particle size.

The method for incorporating the crosslinked polymer particles used in the present invention into the polyester is not particularly limited,
A known method can be adopted. For example, when the particles are obtained as an ethylene glycol slurry dispersion, they are added at any stage of the polyester production process, preferably after the esterification or transesterification reaction and before the polycondensation reaction is started, and the polycondensation reaction is advanced. And good. Also,
If necessary, other particles, for example, particles of silica, kaolin, talc, calcium carbonate, aluminum oxide and the like can be used in combination within a range not impairing the gist of the present invention. In particular, it is preferable to use other particles having a larger particle size than the crosslinked polymer particles used in the present invention together, because the running property of the film is further improved. The coating layer in the present invention is made of a water-soluble or water-dispersible resin such as polyester resin, vinyl chloride / vinyl acetate copolymer resin, ether resin, butadiene resin, acrylic resin, urethane resin, or cellulose resin. It can be obtained by applying a coating solution containing at least one selected resin and drying it. Among these resins, urethane resins and polyester resins are particularly preferable.

The following polyols, polyisocyanates, chain extenders, cross-linking agents and the like can be exemplified as the components constituting the urethane resin. Examples of polyols include polyethers such as polyoxyethylene glycol, polyoxypropylene glycol and polyoxytetramethylene glycol, polyethylene adipate, polyethylene butylene adipate, polyesters such as polycaprolactone, acrylic polyol, castor oil, etc. Is mentioned. Examples of polyisocyanates include tolylene diisocyanate, phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, isophorone diisocyanate, and the like. Examples of chain extenders or crosslinking agents include ethylene glycol, propylene glycol, diethylene glycol, trimethylolpropane, hydrazine, ethylenediamine, diethylenetriamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodicyclohexylmethane, water and the like. To be

Examples of the component constituting the polyester resin include the following polyvalent carboxylic acids and polyvalent hydroxy compounds. That is, as the polyvalent carboxylic acid, terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 4,4′-diphenyldicarboxylic acid, 2,5-
Naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2-potassium sulfoterephthalic acid, 5-sodiumsulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutaric acid , Succinic acid, trimellitic acid, trimesic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, trimellitic acid monopotassium salt and their ester-forming derivatives can be used. Further, as the polyhydric hydroxy compound, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 2-methyl -1,5-pentanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, p-xylylene glycol, bisphenol A
-Ethylene glycol adduct, diethylene glycol,
Triethylene glycol, polyethylene glycol,
Polypropylene glycol, polytetramethylene glycol, polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolethylsulfonate, potassium dimethylolpropionate and the like can be used.

One or more of these compounds are appropriately selected and a polyester resin is synthesized by a conventional polycondensation reaction. In addition to the above, JP-A-1-1
The polyester-based resin of the present invention also includes a composite polymer having a polyester component such as so-called acrylic graft polyester and polyester polyurethane in which polyester polyol is chain-extended with isocyanate described in Japanese Patent No. 65633. The resin in the present invention is
From the viewpoint of safety and health, it is desirable that the coating agent uses water as a medium, but within a range not exceeding the gist of the present invention, an organic solvent is used for the purpose of improving dispersibility in water or improving film-forming performance. It may be contained. Examples of the organic solvent include alcohols such as isopropyl alcohol and ethyl alcohol, diols such as ethylene glycol and diethylene glycol, glycol derivatives such as ethyl cellosolve and n-butyl cellosolve, ethers such as dioxane and tetrahydrofuran, acetic acid esters such as ethyl acetate. , Methyl ethyl ketone and other ketones, and N-methylpyrrolidone and other amides, but are not limited thereto.

When water is used as a medium, it may be a coating agent forcibly dispersed with a surfactant or the like, but preferably a hydrophilic nonionic component such as polyethers,
It is a self-dispersion type coating agent having a cationic group such as a quaternary ammonium salt, and more preferably a water-soluble or water-dispersible coating agent having an anionic group. The water-soluble or water-dispersible coating agent having an anionic group is a compound having a compound having an anionic group bound to a resin by copolymerization or grafting, and sulfonic acid, carboxylic acid, phosphoric acid and their It is appropriately selected from salts and the like.
In order to impart water solubility to the resin, it is preferable to use an alkali metal ion as the counterion of the anionic group, but the counterion of the anionic group is an amine-based one containing ammonium ion from the viewpoint of the heat and humidity resistance of the capacitor described later. It is preferably selected from onium ions. The amount of the anionic group of the water-soluble or water-dispersible coating agent having the anionic group is preferably in the range of 0.05 to 15% by weight, more preferably 0.1 to 10% by weight. And particularly preferably in the range of 0.5 to 8% by weight. When the amount of the anionic group is less than 0.05% by weight, the water solubility or water dispersibility of the resin tends to be poor, and the amount of the anionic group is 15% by weight.
If it exceeds, the water resistance of the undercoat layer after coating may be poor, or moisture absorption may cause the films to stick to each other, or the wet heat resistance may be deteriorated.

The coating liquid in the present invention contains an isocyanate compound as a cross-linking agent in order to improve the adhesion (blocking property), water resistance, solvent resistance and mechanical strength of the coating layer,
Contains epoxy compounds, amine compounds, aziridine compounds, silane coupling agents, titanium coupling agents, zirco-aluminate coupling agents, peroxides, heat and photoreactive vinyl compounds and photosensitive resins. May be. Further, in order to improve stickiness and slipperiness, silica, silica sol, alumina, alumina sol, zirconium sol, kaolin, talc, calcium carbonate, calcium phosphate, titanium oxide, as inorganic fine particles in the coating liquid,
Barium sulfate, carbon black, molybdenum sulfide, antimony oxide sol, etc. are used as organic fine particles such as polystyrene, polyethylene, polyamide, polyester, polyacrylic ester, epoxy resin, silicone resin,
A fluororesin or the like may be contained within the range of the surface roughness described later. Further, if necessary, the coating layer contains an antifoaming agent, a coating property improving agent, a thickener, an antistatic agent, an organic lubricant, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, a pigment, etc. You may have.

The content of alkali metal in the coating solution is preferably 1000 ppm or less, more preferably 500 ppm or less, and particularly preferably 200 ppm or less, based on the solid content of the coating solution. If the content of the alkali metal in the coating solution is high, the wet heat resistance of the capacitor is deteriorated, which is not preferable. It is unavoidable to mix the alkali metal as an impurity in the coating liquid in the preparation process from the raw material synthesis for industrial production. In addition, tap water or groundwater is often used as the commercially available coating agent. Furthermore, it is general that an alkali metal is used as a counter ion of the hydrophilic functional group of the anionic resin preferably used in the present invention in order to make the resin water-soluble. Therefore, a desired coating liquid may be obtained by performing deionization treatment as needed.

A method for applying the above-mentioned coating liquid to a polyester film is described by Yuji Harasaki, Maki Shoten, 1979.
Issued annually, using reverse roll coater, gravure coater, rod coater, air doctor coater or other coating device shown in "Coating Method", it may be applied to the already biaxially stretched film,
Moreover, you may apply | coat in a biaxially stretched film manufacturing process.
As a method of applying in the biaxially stretched film manufacturing process, applied to a polyester film uniaxially stretched in the longitudinal direction,
After stretching in a direction orthogonal to the uniaxial stretching direction further in a dried or undried state, the method of heat treatment, since the film forming and coating drying can be performed at the same time, the merit considering the manufacturing cost is large, especially It is preferably adopted,
It is not limited to this.

In particular, the coating solution is applied to a uniaxially stretched polyester film stretched 2 to 6 times in the longitudinal direction of the film by a roll stretching method at 80 to 170 ° C., and the coating solution is appropriately dried or not dried, and uniaxial polyester film is obtained. Immediately after stretching the stretched film, the film is stretched in the direction perpendicular to the stretching direction by 80 to 170.
2 to 6 times at ℃, 1 to 600 at 150 to 270 ℃
A method of performing heat treatment for seconds is preferable. According to this method, it is possible to dry the coating layer simultaneously with stretching,
The thickness of the coating layer can be reduced according to the draw ratio,
A film suitable as a biaxially stretched polyester film substrate can be manufactured at a relatively low cost. The thickness of the coating layer of the film of the present invention is preferably in the range of 0.01 to 3 μm, more preferably 0.02 to 1 μm. The thickness of the coating layer is preferably thin in view of the demand for miniaturization of the capacitor. However, when the thickness of the coating layer is less than 0.01 μm, it is difficult to obtain a uniform coating layer, so that coating unevenness is likely to occur in the product.

The coating solution according to the present invention may be applied to only one side of the polyester film, or may be applied to both sides. When coated on only one side, a coating layer other than the coating solution of the present invention may be formed on the opposite side, if necessary, to impart other properties to the polyester film of the present invention. In addition, in order to improve the coating property and the adhesive property of the coating agent on the film, the film may be subjected to a chemical treatment or a discharge treatment before the coating. Further, in order to improve the adhesiveness and coatability of the coating layer of the biaxially stretched polyester film of the present invention, the coating layer may be subjected to a discharge treatment after the coating layer is formed. The coating layer formed as described above preferably has a contact angle with water droplets of 60 ° or more. Water droplet contact angle is 6
If it is less than 0 °, the water vapor-deposited film and the water-resistant adhesion are deteriorated,
It may be difficult to provide the capacitor of the present invention with the moisture and heat resistance. Therefore, attention must be paid to the amount of hydrophilic group, the amount of emulsifier, and the amount of hydrophilic compound of the coating agent.

The center line average roughness (Ra) of the coating layer surface of the film of the present invention is in the range of 0.005 to 0.5 μm, more preferably 0.02 to 0.3 μm. , Particularly preferably in the range of 0.05 to 0.1 μm. When Ra is less than 0.005 μm, the slipperiness of the film is insufficient and workability deteriorates. On the other hand, Ra is 0.5
When it exceeds μm, the surface becomes too rough and the withstand voltage characteristic and the moist heat resistance characteristic are deteriorated, which is not preferable. The thickness of the film of the present invention is 5 μm or less, preferably 3 μm or less, more preferably 2 μm or less. Thickness is 5 μm
If it exceeds, it becomes impossible to manufacture a small-sized and large-capacity capacitor, which is not preferable. In the present invention, as the metal to be deposited on the film, aluminum, palladium, zinc, nickel, gold, silver, copper, indium, tin, chromium,
Titanium and the like can be mentioned, but the most preferable metal is aluminum. Note that the above metals include metal oxides. The thickness of the metal vapor deposition film is preferably in the range of 10 to 5000 Å. The vapor deposition method is generally a vacuum vapor deposition method, but may be an electroplating method, a sputtering method, or the like. The metal vapor deposition layer may be provided on both sides of the polyester film. Further, the surface treatment of the vapor-deposited metal layer or the coating treatment with another resin may be performed after the metal vapor deposition.

[0021]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. The evaluation methods in the examples are as follows. In the examples and comparative examples, "part" means "part by weight".

(1) Average Particle Size In the case of cross-linked polymer particles The maximum and minimum diameters of each particle were measured by observing the particles with a scanning electron microscope, and the arithmetic average was taken as the particle diameter (diameter) of each particle. . The particle size was measured for at least 100 particles, and the arithmetic mean thereof was taken as the average particle size. Particles other than cross-linked polymer particles Centrifugal sedimentation type particle size distribution measuring device (SA-CP manufactured by Shimadzu Corporation
Integrated volume fraction 50 in the equivalent spherical distribution measured in 3)
% Particle size was taken as the average particle size. (2) Spherical ratio The maximum diameter and the minimum diameter of each particle are measured by observing the particles with a scanning electron microscope, and the ratio of the maximum diameter / minimum diameter is calculated. The ratio is calculated for at least 100 particles, and the phase of those values is calculated. The arithmetic mean was defined as the spherical ratio.

(3) Deformation Degree of Particles A small piece of a stretched film containing particles was fixed and molded with an epoxy resin, cut with a microtome, and the cross section of the film in the longitudinal direction (longitudinal direction) was observed by a transmission electron microscope. . For particles present within 5 μm from the film surface, the maximum diameter and the minimum diameter are measured for each particle to calculate the ratio of the maximum diameter / minimum diameter, and the ratio is calculated for at least 100 particles, and the values are added together. The average was defined as the deformation ratio. (4) Roughness of coated surface of film surface (center line average roughness R
a) According to the method described in Japanese Industrial Standard JIS B0601, a surface roughness measuring device (SE-3 manufactured by Kosaka Laboratory Ltd.)
The center line average roughness Ra was obtained using F). (5) Film runnability The film was evaluated for slipperiness. The slidability is 53 g (T) when the film is wound around a fixed hard chrome-plated metal roll (diameter 6 mm) at an angle (θ) of 135 °.
The load of ₂ ) was applied to one end and run at a speed of 1 m / min, the resistance force (T ₁ , g) at the other end was measured, and the friction coefficient (μd) during running was determined by the following formula.

[0024]

[Equation 1] (6) Analysis of alkali metal ions Li, Na, K, Rb, Cs, and Fr were quantified by a calibration curve method using an atomic absorption spectrometer (Spectro AA) manufactured by Varian. (7) Water Droplet Contact Angle A contact angle meter (CA-DT-A type, manufactured by Kyowa Interface Science Co., Ltd.) was used to measure the contact angle between the sample film and distilled water in an atmosphere of temperature 23 ° C. and humidity 50% RH. Measured. The contact angle is
A total of 6 points were measured with 2 points on the left and right and 3 points on the number of samples. The diameter of the water droplets was 2 mm, and 1
The number after a minute was read.

(8) Withstand Voltage Characteristics Measurement was carried out according to JIS C-2319. That is, using a 10 kV DC withstanding voltage tester, 23 ° C, 50%
In a RH atmosphere, the voltage was raised at a pressure rising rate of 100 V / sec and the voltage when the film was broken and short-circuited was read. (9) Change in capacitance No-load test A capacitor is 1000 at 60 ° C and 95% RH.
The sample was left for a period of time, and the rate of change in capacitance was calculated using the initial capacitance as a reference value. That is, the value obtained by subtracting the initial capacitance from the capacitance after 1000 hours was divided by the initial capacitance and expressed as a percentage. Load test While applying a DC voltage of 60 V / μm between the electrodes of the capacitor, 100% in an atmosphere of a temperature of 60 ° C. and a humidity of 95% RH.
The sample was allowed to stand for 0 hour, and the capacitance change rate was calculated using the initial capacitance as a reference value. That is, the value obtained by subtracting the initial capacitance from the capacitance after 1000 hours was divided by the initial capacitance and expressed as a percentage.

Example 1 [Production of crosslinked polymer particles] To 2000 parts of demineralized water, 1.6 parts of a water-soluble polymerization initiator potassium persulfate and 0.002 part of sodium lauryl sulfate as a dispersion stabilizer were added to homogenize the mixture. After dissolution, a mixed solution of 20 parts of methyl methacrylate, 30 parts of divinylbenzene and 50 parts of ethylene glycol dimethacrylate was added. Then, polymerization was carried out at 75 ° C. for 7 hours under stirring in a nitrogen gas atmosphere to obtain particles having an average particle size of 0.30 μm and a spherical ratio of 1.05. Next, ethylene glycol 20 was added to an aqueous slurry of the obtained particles.
00 parts was added and heated, and water was distilled off under reduced pressure.

[Production of Polyester] 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate were placed in a reactor, heated and heated, and methanol was distilled off to carry out a transesterification reaction. It took 4 hours from the start to raise the temperature to 230 ° C. to substantially end the transesterification reaction. Next, 0.5 part of the above cross-linked polymer particles was added as an ethylene glycol slurry, 0.03 part of phosphoric acid and 0.04 part of antimony trioxide were further added to carry out a polycondensation reaction, and a polyethylene having an intrinsic viscosity of 0.61 was added. I got terephthalate.

[Production of Polyester Film] The obtained polyethylene terephthalate was extruded at 285 ° C. into a sheet form by an extruder, and an amorphous sheet was obtained by an electrostatic applied cooling method. Stretched and subsequently composed of 100 parts of water-dispersed polyurethane (manufactured by Dainippon Ink and Chemicals, Inc., trade name HYDRAN AP40) having carboxylic acid ammonium salt as a functional group (solid content weight, hereinafter the same), and water as a medium. After applying the coating agent to one side, it is stretched 4.0 times in the transverse direction at 110 ° C. and 220
Heat fixing at ℃, while winding 4% in the longitudinal and transverse directions while relaxing, to obtain a coating layer thickness of 0.04 μm,
A biaxially stretched polyethylene terephthalate film having a film thickness of 1.5 μm was obtained. The content of alkali metal in the coating liquid was 44 ppm of Na and 6 ppm of K in terms of solid content of the coating liquid, and other alkali metals were below the detection limit. The contact angle of water droplets on the coating layer was 63 °, and the center line average roughness (Ra) was 0.020 μm.

[Production of Capacitor] On the coated surface of the obtained film, a resistance heating type metal vapor deposition apparatus was used, and the pressure in the vacuum chamber was set at 10 ⁻⁴ Torr or less, and aluminum was added at 450 ° C.
It was deposited to a thickness of Å. At that time, the polyester film was vapor-deposited in a stripe shape having a margin portion in the longitudinal direction (a vapor deposition portion width of 8 mm and a margin portion width of 1 mm were repeated). The obtained vapor-deposited polyester film was slit into a tape shape having a width of 4.5 mm having a margin portion having a width of 1 mm on the left or right. The vapor deposition film obtained had excellent adhesiveness in the evaluation of adhesiveness.

Each of the obtained vapor-deposited polyester films of the left margin and the right margin was wound together,
I got a roll. At this time, the vapor deposition part is 0.5 m in the width direction.
The two films were wound while being shifted so as to protrude by m. This wound body is heated at a temperature of 150 ° C. and a pressure of 50 kg / cm ^2.
And pressed for 5 minutes. After spraying metallicon on both end faces of this and applying a lead wire, an impregnation layer of a liquid bisphenol A type epoxy resin and a powdered epoxy resin are heat-melted to form an exterior having a minimum thickness of 0.5 mm, A film capacitor having an electrostatic capacity of 0.1 μF was used.
The workability of the capacitor manufacturing process was good. The obtained metal vapor deposition film capacitor was, as shown in Table 1 below, a metal vapor deposition film capacitor having excellent withstand voltage characteristics, little change in capacitance, and excellent moisture and heat resistance characteristics.

Example 2 [Production of crosslinked polymer particles] To 2000 parts of demineralized water, 1.0 part of water-soluble polymerization initiator potassium persulfate and 0.002 part of sodium lauryl sulfate as a dispersion stabilizer were added to homogeneity. After dissolution, a mixed solution consisting of 50 parts of styrene, 30 parts of methyl methacrylate and 20 parts of divinylbenzene was added. Then, with stirring under a nitrogen gas atmosphere, 75
Polymerization was carried out at 0 ° C. for 10 hours to obtain particles having an average particle size of 0.7 μm and a spherical ratio of 1.1. Next, 2000 parts of ethylene glycol was added to the obtained water slurry of the particles, and the mixture was heated and the water was distilled off under reduced pressure.

[Production of Polyester] Polyethylene terephthalate containing particles having an intrinsic viscosity of 0.61 was obtained in the same manner as in Example 1 except that 0.3 part of the crosslinked polymer particles were added as an ethylene glycol slurry. [Production of Polyester Film] A biaxially stretched polyethylene terephthalate film having a coating layer thickness of 0.04 μm and a film thickness of 1.5 μm was obtained in the same manner as in Example 1 except that the above polyethylene terephthalate was used. [Manufacture of Capacitor] A metal-deposited film capacitor was obtained in the same manner as in Example 1 except that the above biaxially stretched polyethylene terephthalate film was used, and its characteristics were evaluated.

Example 3 Instead of the coating agent of Example 1, an aqueous solution containing 80 mol% of isophthalic acid, 15 mol% of sebacic acid, 5 mol% of sodium sulfoisofuric acid, 75 mol% of ethylene glycol and 25 mol% of diethylene glycol. A metal-deposited film capacitor was obtained in the same manner as in Example 1 except that a coating liquid containing 100 parts of a water-soluble polyester as a medium was applied.

Example 4 Instead of the coating agent of Example 1, a water-dispersible polyurethane having a carboxylic acid ammoxame salt as a functional group (manufactured by Dainippon Ink and Chemicals, Inc., trade name HYDRAN AP40) 80
Parts, 20 parts of a water-dispersible polyester (polyester WR-961, trade name, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) having a carboxylic acid ammonium salt as a functional group, except for applying a coating solution using water as a medium. , As in Example 1,
A metal evaporated film capacitor was obtained.

Example 5 The same as Example 1 except that 0.5 part of crosslinked polymer particles having a particle size of 0.30 μ and 0.01 part of spherical silica having a particle size of 0.60 μ were added as an ethylene glycol slurry. , Coating layer thickness 0.04μm, film thickness 1.5μ
A biaxially-stretched polyethylene terephthalate film of m was obtained, and further a metal vapor deposition film capacitor was obtained, and the characteristics were evaluated.

Comparative Example 1 The particles contained in the film have an average particle size of 0.30 μm.
A polyethylene terephthalate film having a film thickness of 1.5 μm was obtained in the same manner as in Example 1 except that m spherical silica was used, and further a metal evaporated film capacitor was obtained. Comparative Example 2 The particles contained in the film have an average particle diameter of 1.2 μm.
A polyethylene terephthalate film having a film thickness of 1.5 μm was obtained in the same manner as in Example 2 except that the porous silica of Example 1 was used, and further a metal evaporated film capacitor was obtained.

Comparative Example 3 To 2000 parts of demineralized water, 1.0 part of water-soluble polymerization initiator potassium persulfate and 0.002 part of sodium lauryl sulfate as a dispersion stabilizer were added and uniformly dissolved, and then 20 parts of styrene. , 15 parts of methyl methacrylate and 65 parts of divinylbenzene were added. Then, polymerization was carried out at 75 ° C. for 15 hours while stirring in a nitrogen gas atmosphere to obtain particles having an average particle size of 0.7 μm and a spherical ratio of 1.1.
Next, ethylene glycol 2 was added to the water slurry of the obtained particles.
000 parts was added and heated, and water was distilled off under reduced pressure. A biaxially stretched polyethylene terephthalate film having a film thickness of 1.5 μm was obtained in the same manner as in Example 2 except that the above cross-linked polymer particles were used, and further a metal evaporated film capacitor was obtained.

Comparative Example 4 [Production of Crosslinked Polymer Particles] To 2000 parts of demineralized water, 1.0 part of water-soluble polymerization initiator potassium persulfate and 0.002 part of sodium lauryl sulfate as a dispersion stabilizer were added to homogenize them. After dissolution, a mixed solution consisting of 80 parts of styrene, 10 parts of methyl methacrylate and 10 parts of divinylbenzene was added. Then, with stirring under a nitrogen gas atmosphere, 75
Polymerization was performed at 8 ° C. for 8 hours to obtain particles having an average particle size of 0.7 μm and a spherical ratio of 1.1. Next, 2000 parts of ethylene glycol was added to a water slurry of the obtained particles, and the mixture was heated and the water was distilled off under reduced pressure. A biaxially stretched polyethylene terephthalate film having a film thickness of 1.5 μm was obtained in the same manner as in Example 2 except that the above cross-linked polymer particles were used, and further a metal evaporated film capacitor was obtained.

Comparative Example 5 A biaxially stretched polyethylene terephthalate film having a thickness of 1.5 μm was obtained in the same manner as in Example 1 except that the coating agent was not applied to the surface of the film, and further a metal evaporated film capacitor was obtained. It was Comparative Example 6 The amount of Na in the coating liquid was 2000 ppm in terms of solid content, K
Example 1 except that the amount of the coating solution is 6 ppm in terms of solid content and the other alkali metals are below the detection limit.
In the same manner as in (1), a biaxially stretched polyethylene terephthalate film having a thickness of 1.5 μm was obtained, and further a metal evaporated film capacitor was obtained. The results obtained above are summarized in Tables 1 to 4 below.

[0040]

[Table 1] Table 1 ──────────────────────────────────── Example 1 Example 2 Example 3 ──────────────────────────────────── <Additive particles> Particle type Crosslinked polymer particles Crosslinked polymer Particles Cross-linked polymer particles Average particle diameter (μm) 0.30 0.70 0.30 Particle content (wt%) 0.5 0.3 0.5 Spherical ratio 1.05 1.1 1.05 Deformation ratio 1 .2 1.5 1.2 <Film characteristics> Thickness (μm) 1.5 1.5 1.5 Coating surface Ra (μm) 0.020 0.020 0.020 Running property (friction coefficient) 0.42 0 .35 0.43 Water droplet contact angle (°) 63 63 62 Alkali metal content in coating agent (ppm) Na 44 44 160 K 6 6 9 Others below detection limit below detection limit below detection limit <Capacitor characteristics> Withstand voltage (kv / μm) 0.70 0.60 0.70 Capacity change rate (%) No load 0.4 0.4 0.4 Load 0.4 0.4 −0.5 ─ ───────────────────────────────────

[0041]

[Table 2] Table 2 ──────────────────────────────────── Example 4 Example 5 Comparative Example 1 ──────────────────────────────────── <Additive particles> Particle type Crosslinked polymer Crosslinked polymer Spherical Silica particles Particles / spherical silica Average particle diameter (μm) 0.30 0.30 / 0.60 0.30 Particle content (wt%) 0.5 0.5 / 0.01 0.5 Spherical ratio 1.05 1.05 / 1.02 1.05 Deformation ratio 1.2 1.2 / 1.02 1.05 <Film characteristics> Thickness (μm) 1.5 1.5 1.5 1.5 Coating surface Ra (μm) 0.020 0.020 0.020 Running property (friction coefficient) 0.42 0.30 0.36 Water droplet contact angle (°) 63 63 63 63 Content of alkali metal in coating agent (ppm) Na 50 50 44 K 10 10 6 Others Detection limit or more Below detection limit Below detection limit <Capacitor characteristics> Withstand voltage (kv / μm) 0.70 0.69 0.35 Capacity change rate (%) No load 0.4 0.4-5 Load 0.1 0.1- 10 ────────────────────────────────────

[0042]

[Table 3] Table 3 ──────────────────────────────────── Comparative Example 2 Comparative Example 3 Comparative Example 4 ──────────────────────────────────── <Additive particles> Particle type Porous silica Crosslinked polymer particles Crosslinked polymer particles Average particle size (μm) 1.2 0.70 0.70 Particle content (wt%) 0.3 0.3 0.3 Spherical ratio-1.1 1.1 Deformation ratio-1.12. 3.0 <Film characteristics> Thickness (μm) 1.5 1.5 1.5 1.5 Coating surface Ra (μm) 0.020 0.020 0.020 Running property (friction coefficient) 0.32 0.37 0.60 Water drop contact angle (°) 63 63 63 63 Content of alkali metal in coating agent (ppm) Na 44 44 44 44 K 6 6 6 Others below detection limit below detection limit below detection limit <conden Sir characteristics> Withstand voltage (kv / μm) 0.40 0.42 0.55 Capacity change rate (%) No load -2 -4 0.8 Load -8 -7 0.9 ───────── ────────────────────────────

[0043]

[Table 4] Table 4 ──────────────────────────────────── Comparative Example 5 Comparative Example 6 ── ────────────────────────────────── <Additive particles> Particle type Crosslinked polymer particles Crosslinked polymer particles Average particle Diameter (μm) 0.30 0.30 Particle content (wt%) 0.5 0.5 Spherical ratio 1.05 1.05 Deformation ratio 1.2 1.2 <Film property> Thickness (μm) 1.5 1.5 Coating surface Ra (μm) 0.020 0.020 Running property (friction coefficient) 0.43 0.42 Water droplet contact angle (°) 62 63 Alkali metal content in coating agent (ppm) Na 160 2000 K 9 6 Others Below detection limit Below detection limit <Capacitor characteristics> Withstand voltage (kv / μm) 0.60 0.60 Capacity change rate (%) No load -10 -4 Load −45 −18 ────────────────────────────────────

[0044]

INDUSTRIAL APPLICABILITY The biaxially stretched polyester film of the present invention, when used as a base film of a metallized film capacitor, exhibits excellent withstand voltage characteristics and wet heat resistance characteristics and contributes to improvement of long-term reliability of the capacitor. And its industrial value is high.

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Claims (1)

[Claims] 1. Crosslinked polymer particles having an average particle diameter of 0.1 to 2 μm, a spherical ratio of 1.0 to 1.2, and a degree of particle deformation after biaxially stretching a film of 1.05 to 2.5. A biaxially stretched polyester film containing 0.1 to 2% by weight,
At least one surface of the film has a coating layer made of a water-soluble or water-dispersible resin, and the coating layer has a surface roughness Ra of 0.0
A biaxially stretched polyester film for capacitors, which has a thickness of 05 to 0.5 μm and a total thickness of 5 μm or less.